Architecture :: Ado.net Entity Framework - Query - Return Correct Data

I just tring to a complex (for me) with ado.net entity framework this is the structure: In practice it is a sort of group purchasing (Buyers) For each group of purchase (Buyer) should have the opportunity 'to select all products of the brands indicated in buyer I'm doing function to return correct data like this:

public List<Product> GetProductsByBuyer(int vBuyerId)
{
Buyersctx.Products.MergeOption = MergeOption.NoTracking;
return (from lProduct in Buyersctx.Products.Include("Brand").Include("Buyers")
where select lProduct).ToList();
}